Take it from someone that has the tune from BMS that Mike mentioned right now, that my gas mileage has not been impacted, and to the contrary, I've seen an improvement (considering the way I've been driving with the tune, my gas mileage hasn't suffered).

There are 2 other companies that have tunes available: DTUK (2) and VAC (1).

Quote:

Originally Posted by vasillalov

Here is a software upgrade for your ECU made by a highly reputable BMW tuner: